We have shown that storage of human platelets at 4 degrees C for 24 hrs results in a considerable reduction in their oxidative activity towards fatty acids, glucose, and certain Krebs cycle substrates. Hypoosmolarity induces hyperpermeability of the platelet outer membrane and mitochondria towards certain small molecules. Glucose and Krebs cycle substrates can be made to leak inwards; and (-)-carnitine, towards. Obviously these observations are important from a theoretical point of view. But, and particularly with respect to platelet preservation, there is the intriguing possibility that hypotonic media may prolong shelf life of platelets by allowing their mitochondria greater access to energy substrates and preservation additives. And, since respiration is a more efficient energy yielding process than glycolysis, it is possible that maintenance of the former is the more imperative for platelet viability. We propose further study of 1) the cofactors and optimal conditions (temperature, pH, osmolarity) for oxidative activity of platelets towards glucose, fatty acids, and all of the Krebs cycle intermediates. Efforts will be made to compare glycolytic and HMP shunt activity under the same conditions and to define control mechanisms governing the interrelationship of the three path-ways. Particular attention will be paid to determining the effect of hypoosmolarity on these control mechanisms. ATP levels and the coupling of oxidative phosphorylation at various osmolarities will also be measured; 2) using the data from 1) for comparison, the effect of various anticoagulants (AVD, CPD, ACD- adenine, IAG) will be determined; 3) using the data from 1 and 2, the effect of various storage (1 degree C, 22 degrees C, 37 degrees C; platelet rich plasma, whole blood) and preservation (controlled slow freezing in glycerol- or dimethysulfoxide-containing media) methods will be determined; 4) using the data of 1-3, the effect of "new" additives, in combination with various anticoagulants and osmolarities on storageability will be determined. It is possible, for example, to envision an enhanced effect of adenine in hypoosmolaric storage media. Another possibility is that (-)-carnitine may be useful to combine with hypoosmolaric media to allow for the successful maintenance of fatty acid oxidation along with enhanced glucose oxidation.